Surface Acoustic Wave (SAW)(lateral mode) filters and bulk acoustic wave (BAW)(vertical mode) filters are being manufactured and are suitable for low/mid and mid/high long-term evolution (LTE) mobile bands, respectively. Lamb-wave (lateral mode) filters are not yet being manufactured, but are theoretically promising. However, SAW filters are stand alone and not extendable to LTE high and 5th generation (5G) bands; a BAW filter's center frequency is determined by the thickness of the thin-film piezoelectric layer, e.g., aluminum nitride (AlN), so integrating multiple frequencies on a single chip requires repeated masking and thinning of the thin-film piezoelectric layer with associated tolerance and cost degradation; and Lamb-wave filters have an unacceptable low coupling coefficient (k2eff), which precludes commercial use. Further, known acoustic wave filters are often susceptible to warping/buckling and excessive center frequency variability.
A need therefore exists for methodology enabling formation of an acoustic wave filter with a relatively high k2eff and large bandwidth, reduced beam bending variability and improved center frequency variability, and a high electromechanical k2eff enabling commercial use and the resulting device.